Coolant Replacement Question

[MHarryE]

My Kubota M7 manual maintenance schedule is to replace coolant every 2 years. Mine is now 7 years old and I decided to replace even though test strips said the original coolant was in excellent condition. I went by the manual except for flushing the system - based on test strip results and logic that not all of the coolant will drain - the book is specific on how to empty the system. Refilling was exactly to book procedure except I was needed about 1 gallon less than the instructions said. Book stated all systems will drain down but I looked at the parts diagram and understood that is not possible - coolant is directed to the DEF tank heater which has a lot of coils meaning a lot of coolant below the drain point will never be drained. If I go by coolant capacity vs the amount needed to refill, I think I replaced about 85%. So instead of all new coolant, I have remaining coolant of a different type (2016 coolant types when my tractor was built are no longer available). That makes coolant change unlike engine oil change where most of the oil is replace, and instead like hydraulic oil replacement where oil in the loader cylinders, hoses, sumps of various components, etc., is not drained. Has anyone ever replaced coolant and had a problem with coolant compatibility? The book states only to use an ethylene glycol based coolant which I did - Caterpillar Extended Life Coolant.

 

[Snobdds]

Drain coolant
Fill with Distilled water
Run to get it hot.
Drain again
Fill with new coolant at 50% of capacity.
Fill to top with distilled water.

If you really want to do it right, add one more distilled water flush.

Coolant is just as important as oil for engine health. Coolant turns acidic and as a result, a low volt battery. It will eat through aluminum and the dropping of silicates in solution will also cause cavitation.

There is a reason they want you to change it every two years. But the damage might be done...

 

[RjCorazza]

I have always done multiple flushes with tap water, followed by one flush with distilled water when changing coolant chemistries.
FYI, Cat says mixing their ELC coolant with standard coolants at greater than 10% standard coolant reduces the service interval to that of the standard coolant. There is no mention of any other problems.